1. Field of the Invention
The present invention relates to an object, a method, or a manufacturing method. In addition, the present invention relates to a process, a machine, manufacture, or a composition of matter. In particular, the present invention relates to, for example, a semiconductor device, a display device, a light-emitting device, a power storage device, a memory device, a driving method thereof, or a manufacturing method thereof. In particular, the present invention relates to a semiconductor device including an oxide semiconductor, and a method for manufacturing the semiconductor device.
In this specification, a semiconductor device generally means a device which can function by utilizing semiconductor characteristics. For example, a memory device, an electro-optical device, a semiconductor circuit, and an electronic device may include a semiconductor device.
2. Description of the Related Art
A technique by which transistors are formed using semiconductor thin films formed over a substrate having an insulating surface has been attracting attention. Such transistors are applied to a wide range of electronic devices such as an integrated circuit (IC) and an image display device (display device).
A silicon-based semiconductor material is widely known as a material for a semiconductor thin film applicable to a transistor. As another material, an oxide semiconductor has been attracting attention.
For example, a transistor including a semiconductor layer formed using an oxide containing indium (In), gallium (Ga), and zinc (Zn) (an In—Ga—Zn-based oxide) is disclosed (e.g., see Patent Document 1).
Further, in particular, for a highly integrated electronic device with high performance, a transistor is required to be miniaturized, and a vertical transistor structure in which reduction in an area occupied by the transistor is achieved has been proposed (e.g., see Patent Document 2).